The subject matter disclosed herein relates to systems and methods for providing a well-mixed dry feed of fuel to a gasification system.
Synthesis gas, or syngas, is a mixture of hydrogen (H2) and carbon monoxide (CO) that can be produced from carbonaceous fuels. Syngas can be used directly as a source of energy (e.g., in combustion turbines), or can be used as a source of starting materials for the production of other useful chemicals (e.g., methanol, formaldehyde, acetic acid). Syngas is produced in large scale by gasification systems, which include a gasification reactor or gasifier that subjects a carbonaceous fuel, such as coal, and other reactants to certain conditions to produce an untreated or raw syngas. To increase the efficiency of the gasification reaction, the stoichiometric ratio of coal to water within the gasifier is typically maintained within a desired range.
Coal may be collected from various sources, which can lead to different ranks, or qualities, of the coal. Generally, low-rank coals will have higher water content, while high-rank coals have a lower water content. Unfortunately, the variance in water content from one rank of coal to another may reduce the ability to produce syngas using a single set of conditions for all types of coal. For example, in conditions where low-rank coals are used, the estimation of the water content of the coal may not be accurate, which can lead to inefficiencies during gasification of the low-rank coal. That is, a portion of the heat provided to the gasifier for driving the gasification of the carbonaceous fuel within the low-rank coal may be instead used to produce steam from the water of the coal. Further, these coals may have an inconsistent energy content, where the coal may include regions having large amounts of moisture and low fuel content, and other regions having relatively small amounts of moisture and relatively concentrated fuel content. These inconsistencies can reduce the efficiency of the gasifier, reduce the life of the gasifier and associated equipment, and reduce the predictability of the syngas (e.g., the energy content of the syngas).